When batteries or equivalent DC sources are used to supply power to one or more DC motors as in electric vehicles, for example, the control of energization of the motors poses serious problems. Silicon controlled rectifiers as used in prior circuits have a serious disadvantage because they have the characteristic that once they are turned on, i.e., once they are conductive, they cannot be turned off or made nonconductive through a signal applied to the gate or control electrode thereof. As a result, it has been necessary to combine such rectifiers with transformers, inductors and/or other expensive components when used in controlling energization of DC motors from sources other than AC sources. Transistors have problems with respect to power loss therewithin and when high currents must be handled, they become quite expensive. Mechanical controllers also have problems especially with regard to wear, arcing and breakdown.